U.S. patent application number 11/415089 was filed with the patent office on 2007-07-05 for linear ac/dc power adapters.
Invention is credited to Juan Carlos Corona Ochoa.
Application Number | 20070153557 11/415089 |
Document ID | / |
Family ID | 38224174 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070153557 |
Kind Code |
A1 |
Ochoa; Juan Carlos Corona |
July 5, 2007 |
Linear AC/DC power adapters
Abstract
An AC/DC power adapter comprising a transformer and a rectifier
bridge. The rectifier bridge replaces the conventional diodes with
Schottky diodes. Due to a low voltage drop, the heat dissipated by
the rectifier bridge is decreased and the power efficiency of the
rectifier bridge is significantly increased.
Inventors: |
Ochoa; Juan Carlos Corona;
(Richmond, CA) |
Correspondence
Address: |
Michael Bednarek;Pillsbury Winthrop Shaw Pittman LLP
1650 Tysons Boulevard
McLean
VA
22102
US
|
Family ID: |
38224174 |
Appl. No.: |
11/415089 |
Filed: |
May 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60754620 |
Dec 30, 2005 |
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Current U.S.
Class: |
363/125 |
Current CPC
Class: |
H02M 7/06 20130101 |
Class at
Publication: |
363/125 |
International
Class: |
H02M 7/00 20060101
H02M007/00 |
Claims
1. An AC/DC power adapter having an input terminal and an output
terminal, comprising: a transformer coupling to the input terminal
for reducing a level of an AC voltage input; and a rectifier bridge
coupled to an output of the transformer for changing the AC voltage
to an DC voltage after the AC voltage input level is reduced; and
wherein the rectifier bridge is composed of Schottky diodes.
2. The AC/DC power adapter of claim 1, further comprising a
filtering capacitor coupled to the rectifier bridge for filtering
the voltage after rectified.
3. The AC/DC power adapter of claim 1, wherein the output of the
AC/DC power adapter is used for a consumer electronics product.
4. The AC/DC power adapter of claim 1, wherein the AD/DC power
adapter is used in a cordless telephone.
5. The AC/DC power adapter of claim 1, wherein the rectifier bridge
includes four Schottky diodes.
6. The AC/DC power adapter of claim 1, wherein the rectifier bridge
is a full wave rectifier.
7. The AC/DC power adapter of clam 1, wherein the rectifier bridge
includes two Schottky diodes.
8. The AC/DC power adapter of claim 7, wherein the rectifier bridge
is a half wave rectifier.
9. The AC/DC power adapter of claim 1, has a full load efficiency
in the range between about 60% and about 75% when rated at 9 VDC,
600 mA.
10. The AC/DC power adapter of claim 1, has a full load efficiency
in the range between about 59% and about 71% when rated at 9 VDC,
400 mA.
11. The AC/DC power adapter of claim 1, has a full load efficiency
in the range between 56% and 62% when rated at 9 VDC, 200 mA.
12. An AC/DC power adapter, comprising: an input terminal and an
output terminal; a transformer coupling to the input terminal for
reducing a level of an AC voltage input; a rectifier bridge coupled
to an output of the transformer for changing the AC voltage to an
DC voltage after the AC voltage input level is reduced; and a
filtering capacitor coupled to the rectifier bridge for filtering
the voltage after rectified, and wherein the rectifier bridge is
composed of Schottky diodes.
13. The AC/DC power adapter of claim 12, wherein the rectifier
bridge includes four Schottky diodes.
14. The AC/DC power adapter of claim 13, wherein the rectifier
bridge is a full wave rectifier.
15. The AC/DC power adapter of clam 12, wherein the rectifier
bridge includes two Schottky diodes.
16. The AC/DC power adapter of claim 15, wherein the rectifier
bridge is a half wave rectifier.
17. The AC/DC power adapter of claim 12, has a power efficiency in
the range between about 60% and about 75% when rated at 9 VDC, 600
mA and an average power efficiency about 71%.
18. The AC/DC power adapter of claim 12, has a power efficiency in
the range between about 59% and about 71% when rated at 9 VDC, 400
mA and an average power efficiency about 66%.
19. The AC/DC power adapter of claim 12, has a power efficiency in
the range between 56% and 62% when rated at 9 VDC, 200 mA and an
average power efficiency about 59%.
20. The AC/DC power adapter of claim 12, wherein the AC/DC power
adapter is used in a cordless telephone.
21. The AC/DC power adapter of claim 12, wherein the AC/DC power
adapter is used in a consumer electronics product.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/754,620, filed Dec. 30, 2005, which is herein
incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The invention relates generally to a power adapter, and more
particularly, to linear AC/DC power adapters with power
efficiencies.
[0004] 2. Background of the Invention
[0005] A conventional linear AC/DC power adapter that is commonly
used in consumer electronics such as cordless telephones includes a
diode bridge composed of four conventional diodes. The use of
conventional diodes contributes in reducing the adapter power
efficiency, which, along with other component power consumption,
fails to comply with the Appliance Efficiency Regulations
promulgated by California Energy Commission. To solve the problem,
one available technical option is to use switching power adapters.
Such adapters, however, are expensive and may add electrical side
effects to the telephone. Known side effects include, for example,
noise, radiated emissions, and poor isolation between an
electricity main ground and a telephone line ground.
[0006] An improved linear adapter uses a better-quality core for a
transformer to reduce core losses. This improvement results in
AC/AC adapters passing the California regulation, but AC/DC
adapters still do not comply the regulation. Accordingly, there is
still a need for an AC/DC power adapter with higher power
efficiency.
BRIEF SUMMARY OF THE INVENTION
[0007] Certain embodiments of the invention provide an AC/DC power
adapter used in consumer electronics such as cordless telephones.
The AC/DC power adapter replaces conventional diodes of a diode
bridge with Schottky diodes. The use of Schottky diodes reduces the
heat dissipation of the bridge to increase the power
efficiency.
[0008] In some embodiments of the invention, an AC/DC power adapter
includes a transformer for reducing the level of an input AC
voltage, a rectifier bridge coupled to an output of the transformer
for changing the AC voltage to DC voltage after reduced, and a
filter capacitor for reducing the ripple of the voltage after
rectified, wherein the rectifier bridge is composed of four Schotty
diodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a electrical circuitry of an AC/DC power adapter
in accordance with the present invention.
[0010] FIGS. 2-6 are tables showing experimental results.
DETAILED DESCRIPTION OF THE INVENTION
[0011] As illustrated in FIG. 1, a linear AC/DC power adapter 10
includes a linear transformer 11, a rectifier bridge 12, and a
filter capacitor 13. Linear transformer 11 is used to reduce and
isolate an alternating current/voltage (AC) input voltage.
Rectifier bridge 12 is used to convert AC to direct current/voltage
(DC). Filter capacitor 13 is used to reduce the DC voltage
variations or ripple. Conventionally, the rectifier bridge is
composed of four conventional rectifier diodes. Ideally, there is
no energy consumption in the adapter. The energy is just
transferred from the adapter input to the output. However, real
adapters dissipate energy in heat form at linear transformer 11,
rectifier bridge 12, and filter capacitor 13. Linear transformer 11
has energy losses due to its coil resistances and core. Rectifier
bridge 12 consumes energy due to its voltage drop greater than
zero. Filter capacitor 13 has contact and insulator resistance,
which also dissipates heat.
[0012] Embodiments of the present invention use Schottky diodes to
replace the conventional diodes of rectifier bridge 12. Schottky
diodes have smaller voltage drop than conventional diodes. For
example, typical voltage drop values are 0.4V for Schottky diodes
and 0.7V for conventional diodes. This voltage drop reduction
causes less heat dissipation on rectifier bridge 12.
[0013] The use of Schottky diodes instead of conventional diodes in
Linear AC/DC power adapters improves power efficiency. It is a
reliable, economic, and simple way to comply with Appliance
Efficiency Regulations from California Energy Commission (CEC).
Further, by using Schottky diodes, no electrical side effects occur
in AC/DC power adapter 10 so that the reliability of linear
adapters is maintained.
[0014] The use of Schottky is believed never been seen in linear
AC/DC power adapters nor in any technical publication. Due to a
smaller voltage drop of the Schottky rectifier diodes, rectifier
bridge 12 composed of Schottky rectifier diodes potentially
dissipates less energy than conventional rectifier diodes, as it is
proved in FIGS. 2-6.
[0015] FIG. 2 shows test results of three different adapters, rated
at 9 VDC 600 mA, 9 VDC 400 mA, and 9 VDC 200 mA, respectively. All
of the adapters include an improved transformer core and a
conventional rectifier bridge. As shown, a full load efficiency of
all of them is less than a CEC average efficiency.
[0016] FIG. 3 shows test results of the same adapter rated at 9 VDC
600 mA used in the test of FIG. 2, but now with Schottky diodes in
its rectifier bridge. The first row indicates the full load
efficiency is 63.5% that is better than 60.9% with conventional
diodes. Thus, the average efficiency is 71.4%, which is more than a
required efficiency of 65.2%.
[0017] FIG. 4 shows test results of the same adapter rated at 9 VDC
400 mA used in the test of FIG. 2, but now with Schottky diodes in
its rectifier bridge. The first row indicates the full load
efficiency is 59.4% instead of 57.5% with conventional diodes.
Thus, the average efficiency is 65.6%, which is also more than a
required efficiency of 61.5%.
[0018] FIG. 5 shows test results of the same adapter rated at 9 VDC
200 mA used in the test of FIG. 2, but now with Schottky diodes in
its rectifier bridge. The first row of the result indicates the
full load efficiency is 56.8% instead of 53.4% with conventional
diodes. Thus, the average efficiency is 59.0%, which is still more
than a required efficiency of 55.3%.
[0019] FIG. 6 shows test results of a different adapter that is
rated at 9 VDC 400 mA and has an improved transformer core. As
shown, the power efficiency with conventional diodes is not enough
to pass CEC requirement. However, the same adapter with Schottky
diodes instead of conventional diodes passes the CEC requirement
with margin.
[0020] According to the present invention, AC/DC power adapters 10
has at least the following advantages: [0021] (1) No adapter
dimension changes required; [0022] (2) Easy to manufacture; [0023]
(3) Reduce heat dissipation of a whole telephone; and [0024] (4) No
electric side effects, for example no noise added and high
insulation between power main ground and telephone line ground.
[0025] Furthermore, although the rectifier bridge shown in FIG. 1
is composed of four Schottky diodes as a full wave rectifier, the
number of the Schottky diodes is not limited to four. For example,
the rectifier bridge can also be a half wave rectifier, in which
only two Schottky is included in the rectified bridge.
[0026] The foregoing disclosure of the preferred embodiments of the
present invention has been presented for purposes of illustration
and description. It is not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Many variations and
modifications of the embodiments described herein will be apparent
to one of ordinary skill in the art in light of the above
disclosure. The scope of the invention is to be defined only by the
claims appended hereto, and by their equivalents.
[0027] Further, in describing representative embodiments of the
present invention, the specification may have presented the method
and/or process of the present invention as a particular sequence of
steps. However, to the extent that the method or process does not
rely on the particular order of steps set forth herein, the method
or process should not be limited to the particular sequence of
steps described. As one of ordinary skill in the art would
appreciate, other sequences of steps may be possible. Therefore,
the particular order of the steps set forth in the specification
should not be construed as limitations on the claims. In addition,
the claims directed to the method and/or process of the present
invention should not be limited to the performance of their steps
in the order written, and one skilled in the art can readily
appreciate that the sequences may be varied and still remain within
the spirit and scope of the present invention.
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